β-Co(OH) Nanosheets: A Superior Pseudocapacitive Electrode for High-Energy Supercapacitors.

In this work, β-Co(OH) nanosheets are explored as efficient pseudocapacitive materials for the fabrication of 1.6 V class high-energy supercapacitors in asymmetric fashion. The as-synthesized β-Co(OH) nanosheets displayed an excellent electrochemical performance owing to their unique structure, morphology, and reversible reaction kinetics (fast faradic reaction) in both the three-electrode and asymmetric configuration (with activated carbon, AC). For example, in the three-electrode set-up, β-Co(OH) exhibits a high specific capacitance of ∼675 F g at a scan rate of 1 mV s . In the asymmetric supercapacitor, the β-Co(OH) ∥AC cell delivers a maximum energy density of 37.3 Wh kg at a power density of 800 W kg . Even at harsh conditions (8 kW kg ), an energy density of 15.64 Wh kg is registered for the β-Co(OH) ∥AC assembly. Such an impressive performance of β-Co(OH) nanosheets in the asymmetric configuration reveals the emergence of pseudocapacitive electrodes towards the fabrication of high-energy electrochemical charge storage systems.